The objectives of this project are to grow virulent Treponema pallidum in a cell-free medium and to induce immunity to T. pallidum in rabbits. Specific goals are to develop methods for more optimal growth of Treponema hyodysenteriae in cell-free liquid meidum, to attempt to grow virulent T. pallidum under similar conditions as T. hyodysenteriae, to study the basis for O2 consumption by pathogenic treponemes and to develop procedures for infecting rabbits with Mycobacterium bovis (BCG) for the prevention of lesion development by virulent T. pallidum. BIBLIOGRAPHIC REFERENCES: Harris, D. L. and Glock, R. D.: Swine Dysentery. In Diseases of Swine, edited by H. W. Dunne and A. D. Leman. Fourth Edition. Iowa State University Press, Ames. 1975. In press. Harris, D. L., Glock, R. D. and Kinyon, J. M.: Intestinal Treponematoses. Symposium on the Biology of Parasitic Spirochetes, edited by R. Johnson. Academic press. 1976.